Human Papillomaviruses (HPVs) are small nonenveloped DNA viruses involved in many conditions and diseases. For example HPVs cause a wide variety of benign and pre-malignant tumors.
HPV is spread by direct contact. HPVs may be divided into two categories: cutaneous and mucosal. The cutaneous HPVs cause warts on hands and feet, such as common, plantar, filiform, or flat warts. The mucosal HPV types infect the anogenital region and the oral cavity. Approximately 100 different types of HPV have been characterized to date. Approximately 40 HPV types specifically infect the genital and oral mucosa.
Mucosal HPVs are most frequently sexually transmitted and, with an incidence roughly twice that of herpes simplex virus infection, HPVs are considered one of the most common sexually transmitted diseases (STDs) throughout the world. Infection with the human papillomavirus (HPV) may not cause any symptoms and does not always produce visible genital warts. When symptoms do develop, they usually occur 2 to 3 months after infection with the virus. Symptoms have been known to develop, however, from 3 weeks to many years after infection occurs. As such, HPV may be spread unknowingly.
More than 25 HPV types that are implicated in anogenital diseases are broadly classified as either low risk or high risk. Low risk HPVs, such as HPV-6 and HPV-11, are the etiological cause of genital warts (condyloma acuminata). High risk HPVs, such as HPV-16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59, and 68, usually do not produce visible genital warts. Rather the high-risk viral types may be identified by DNA testing. High risk HPVs such as HPV-16 and HPV-18 may be found on Pap screening tests and be related to precancerous cervical cell change, cervical dysplasia, and cervical cancer. In fact, high-risk HPV types, such as 16, 18, 31, 33, and 35, are strongly associated with precancerous and cancerous changes of the cervix. Most cervical cancers (about 90%) contain one of these high-risk types. High risk HPV infection creates a lifetime risk of invasive cancer in the range of 5-10% for untreated infection.
In addition to cervical cancer, high risk HPVs are associated with a number of anal and perianal cancers.
Current treatments for genital warts and cervical dysplasia include physical removal such as cryotherapy, electrosurgery, and surgical excision. Currently, there are no effective antiviral treatments for HPV infection.